This project is a long-term effort aimed at clarifying the evolutionary relationships within the genus Anopheles, the vectors of human malaria. Past progress has included the clarification of the evolutionary status of the species of the North American Maculipennis complex, the mapping of the salivary gland chromosomes of about 30 American and Asiatic species, the discovery that chromosomal banding patterns are subgeneric in nature and that sibling species, although morphologically identical, can be identified by means of the banding patterns of the salivary gland chromosomes. This proposal continues the research on the evolutionary relationships of the South American anopheline mosquitoes, especially those of the subgenus Nyssorhynchus. They form a group of closely related species which can be distinguished only with difficulty by conventional taxonomic means but are easily identified by the banding patterns of the polytene chromosomes. Field work in the Amazon basin will concentrate on salivary gland chromosome slides from allopatric populations and the study of inversion polymorphism. Work will be continued on albitarsis which consists of at least three different sibling species and the relationship of these sibling species to malaria transmission. Major research efforts will be directed toward the study of genetic homologies between populations, the genetic structure of populations, the extent of genetic variability within populations and genetic load and the adaptive significance, if any, of genetic polymorphisms. Using induced copulation we will make all possible crosses among members of closely related species and an additional method of assessment of the degree of genetic affinity. Especial attention will be given to the cytotaxonomic differentiation of vector vs. nonvector populations.